As you probably know, publishing content online is a great way to promote your business. Unfortunately, the things that make information so easy to share online also make it almost impossible to protect your content. Everyone in the world has access to your website. In a matter of seconds someone can copy and republish your text, images, and even video. The internet is like the wild west. There are no real rules, and there's certainly not anyone to enforce rules even if they existed.
So what should you do if you catch someone republishing your content? Normally, the right thing to do is absolutely nothing. You could send the content thief an email letting them know that you aren't happy, but do you really think they'll care? You can even threaten to sue, but it'll be obvious you're bluffing. Unless the content thief runs a major website (like the New York Times or something like that) a lawsuit simply wouldn't be worth your time.
The worst thing you can do (in my opinion) is try to scare people away from stealing your content with a mean and accusatory copyright notice. It's pretty common to see blogs with footers at the bottom that say in all caps something to the effect of, "Don't you dare do anything with this content or I'll sue your pants off. Don't share it. Don't print it. Don't even read it." Notices like these don't scare away thieves, because they know there's nothing you can do. They only scare away the people that might have tried to share your content legitimately (with links back to your site). By posting threatening messages, you're really just treating your honest readers like criminals and that can't possibly be good for you.
So my advice is to just accept the fact that people can do whatever they want with your content. Don't stress out about it because there's nothing you can do.
Additional note: I was doing a little research for this post and saw another blog post point out that most content thieves won't actually take the time to edit the links in your posts. So even if they republish your content, you still may end up winning in the end if you have links back to your site or affiliate links in your posts. Just some food for thought.